Ronald S. Petralia and Ya-Xian Wang have run the Advanced Imaging Core facility of NIDCD since its inception in October 2011. This core is dedicated primarily to collaborating with and training other scientists in NIDCD in studies utilizing transmission electron microscopy (TEM). And we present an annual workshop on TEM as part of the EARssentials program. Some work also is done with other NIH institutes. In addition, Ronald Petralia regularly reviews papers for professional journals and reviews many various documents for NIDCD PIs, reviews grants, writes review papers and letters of recommendation, serves on several NIH committees and helps coordinate lab+office safety for NIDCD (including annual inspections and reports), and performs animal facility inspections as part of his duties in the ACUC. We have had 2 major upgrades to the JEOL JEM-2100 TEM in 2019. In January, we installed a new Gatan OneView camera with greater sensitivity and drift correction. And in July, we replaced the TEM ion pump with a turbo pump. The turbo pump is more reliable and is less sensitive to humidity; it will allow us to begin planned cryo-EM work on this TEM in the coming year. Also, we have been preparing for the addition of a second electron microscope that will be dedicated largely to cryo-EM; it is an FEI (Thermo Fisher) Titan Halo 300 kV TEM. Dennis Winkler, who joined NIDCD and this core in June, 2019, is a top expert on cryo-EM; he will be overseeing the installation of the Halo (by the end of 2019), and will be responsible for cryo-EM for both TEMs. NIDCD: Tom Friedman/Inna Belyantseva lab: We have 2 collaborations that were published in early 2019; in one, we performed immunogold localization of TBC1D24 (ref 1; Risa Tona) and in the other we provided detailed 3D analyses of stereocilia and rootlets associated with TRIOBP mutants (ref 2). We also are planning to collaborate on a new study with Risa Tona in the near future. The Core continues to advise/train Inna Belyantseva on TEM techniques, to optimize ultrastructural studies of hair cells and stereocilia. We also assist Inna with tissue preparation, e.g., freeze substitution and ultramicrotomy. Katie Kindt lab: The Core continues periodically to use TEM to study the hair cells and associated supporting cells of the zebrafish neuromasts and utricle. In 2017 and 2018, we published papers on neuromasts in J. Neurosci. and Nat. Comm., and we have another in revision. Lisa Cunningham lab: We may continue working on effects of heat shock on the release/uptake of exosomes in the utricle, previously involving a collaboration with the postBac IRTA fellow, Nora Welsh, and Andrew Breglio from the lab (an abstract was presented at ARO in February, 2019 by Melanie Barzik, and a manuscript is in revision). Others: We have a paper recently published (2019) in collaboration with a former NIDCD PI, Stephan Brenowitz, and his fellow, Miloslav Sedlacek, using 3D reconstruction with SEM (ref 3). We also provide some assistance to the lab of Bechara Kachar, including review of manuscripts, and help for Willy Sun related to TEM. And we have discussed continuing our previous work with Doris Wu. Other NIH institutes: NINDS: We published a study in 2017 in Neuron, with Wei Lu/Wenyan Han/Jun Li, on two synaptic cell adhesion molecules, Neuroligin 2 and Slitrk3, associated with GABAergic synapse development in the hippocampus. We now have a collaboration on a GABA-receptor auxiliary protein, Shisa7, that is in final review in Science; both of these studies also involved substantial contributions from the lab of Chris McBain in NICHD. Recently, we have been working on another study on Neuroligin 2. Also, we completed a study with Katherine Roche/Richa Lomash on neurolastin function, looking at structural changes in neurons in the brain of the mutant (ref 4; published in 2019); we are planning another study with them on NMDA receptors. NICHD: In 2018, we published a paper with Dax Hoffman/Lin Lin on a potassium channel auxiliary protein, and we are working on a new project, especially examining this proteins function in the aging brain. We also have previous and open studies with 2 more labs in NICHD, both on zebrafish neuromast development, with Katie Drerup/Dane Kawano, and with Ajay Chitnis/Damian Dalle Nogare; we may continue on these. NIA: We published 3 research papers in 2019 with Mark Mattson/Pamela Yao, including one on sonic hedgehog in the postnatal brain (ref 5), and another on the mitochondrial protein, Sfxn3, in neurons (ref 6). The 3rd paper was in collaboration with a former PI and fellow in NIDCD, using 3D reconstruction with SEM (ref 3; see above). In addition, a review that we published in 2018 (ref 7) was reissued as a chapter in a 2019 book (Calcagnotto et al., eds.; Dynamics and Modulation of Synaptic Transmission in the Mammalian CNS). Dr. Mattson retired in May, 2019, but we are continuing research studies, especially related to neuronal mitochondria and exosomes, with Dr. Yao under her new NIA PI, Dimitrios Kapogiannis. NIMH: We have been working with the lab of Zheng Li on 3 studies including ones with Song Jiao on BAD-BAX-caspase-3 cascade control of synaptic vesicle pools via autophagy, Jun Zhao on mitochondrial fission and dysbindin-1 (in review), and with Kaizheng Duan on mitophagy in the amygdala and hippocampus associated with social anxiety. NEI: In 2018, we agreed to perform TEM studies on zebrafish retina, as part of a new K99 proposal for Wei Li/Juan Angueyra-Aristizabal; this also is a collaboration with Katie Kindt of NIDCD; this may continue next year. NHGRI: We continue to work periodically on studies with Nahid Tayebi/Ellen Sidransky on Parkinson and Gaucher diseases. Outside NIH: Recently, we have been reducing our participation in collaborations outside of NIH due to time restrictions; we may continue studies with Martin Horak (Head-Dept. Neurochem., Inst. Exp. Med., Czech Rep.). In addition to collaborations, Ron Petralia has served as a consultant on studies of T. Fujikawa (Japan)-GluRs in hair cell synapses.